Immunophenotyping and Transcriptomic Outcomes in PDX-Derived TNBC Tissue

Cancer tissue functions as an ecosystem of a diverse set of cells that interact in a complex tumor microenvironment (TME). Genomic tools applied to biopsies in bulk fail to account for this tumor heterogeneity while single cell imaging methods limit the number of cells which can be assessed or are very resource intensive. The current study presents methods based on flow cytometric analysis and cell sorting using known cell surface markers (eg, CD184, CD24, CD90) to identify and interrogate distinct groups of cells in triple-negative breast cancer (TNBC) clinical biopsy specimens from patient-derived xenograft (PDX) models. The results demonstrate that flow cytometric analysis allows a relevant subgrouping of cancer tissue and that sorting of these subgroups provides insights on cancer cell populations with unique, reproducible and functionally divergent gene expression profiles. The discovery of a drug resistance signature implies that uncovering the functional interaction between these populations will lead to deeper understanding of cancer progression and drug response. Implications: PDX-derived human breast cancer tissue was investigated at the single cell level and cell subpopulations defined by surface markers were identified which suggest specific roles for distinct cellular compartments within a solid tumor

Photopatterned antibodies for selective cell attachment

We present a phototriggerable system that allows for the spatiotemporal controlled attachment of selected cell types to a biomaterial using immobilized antibodies that specifically target individual cell phenotypes.o-Nitrobenzyl caged biotin was used to functionalize chitosan membranes and mediate site-specific coupling of streptavidin and biotinylated antibodies after light activation. The ability of this system to capture and immobilize specific cells on a surface was tested using endothelial-specific biotinylated antibodies and nonspecific ones as controls. Homogeneous patterned monolayers of human umbilical vein endothelial cells were obtained on CD31-functionalized surfaces. This is a simple and generic approach that is applicable to other ligands, materials, and cell types and shows the flexibility of caged ligands to trigger and control the interaction between cells and biomaterials.We thank Martina Knecht (MPIP) for help with the synthesis of caged biotin and Dr. Ron Unger and Prof. C. J. Kirkpatrick (University Clinic Mainz, RepairLab) for providing HUVECs. C.A.C. acknowledges funding support from the Portuguese Foundation for Science and Technology (FCT) (fellowship SFRH/BD/61390/2009) and from the International Max-Planck Research School in Mainz. The research leading to these results has received funding from the European Union's Seventh Framework Programme (FP7/2007-2013) under grant agreement no. REGPOT-CT2012-316331-POLARIS